I like the way it looks and all, but as the person above said it looks like a waste of deck space. I would think it would be better to have one of the original Gengar's, with it's poke-power being the same as Spiritomb's attack, and then it has Dark Mind to deal an extra 10 dmg to a benched pokemon, on top of the 30 dmg it does to the defending pokemon.
But it would be kind of stupid to listen to me, since I haven't bought new cards since Neo Genesis, I think. So i'm not even sure if they allow you to use the old cards in tournies and such.
However, I have thought about going to target and getting me a few Majestic Dawn and Legendary Encounters packs for the hell of it.